/*
 * @Author: szx
 * @Date: 2020-05-08 10:16:18
 * @LastEditTime: 2022-02-14 16:55:32
 * @Description:
 * @FilePath: \learn\MDN_JS学习\bouncing-balls-start\main.js
 */
// 定义弹球计数变量
const para = document.querySelector('p');
let count = 0;

// 设置画布

const canvas = document.querySelector('canvas');
const ctx = canvas.getContext('2d');

const width = (canvas.width = window.innerWidth);
const height = (canvas.height = window.innerHeight);

// 生成随机数的函数

function random(min, max) {
    const num = Math.floor(Math.random() * (max - min)) + min;
    return num;
}

function randomColor() {
    return 'rgb(' + random(0, 255) + ', ' + random(0, 255) + ', ' + random(0, 255) + ')';
}

function Shape(x, y, velX, velY, exists) {
    this.x = x;
    this.y = y;
    this.velX = velX;
    this.velY = velY;
    this.exists = exists;
}
function Ball(x, y, velX, velY, exists, color, size) {
    Shape.call(this, x, y, velX, velY, exists);

    this.color = color;
    this.size = size;
}

Ball.prototype = Object.create(Shape.prototype);
Ball.prototype.constructor = Ball;

Ball.prototype.draw = function () {
    ctx.beginPath();
    ctx.fillStyle = this.color;
    ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
    ctx.fill();
};

Ball.prototype.update = function () {
    if (this.x + this.size >= width) {
        this.velX = -this.velX;
    }

    if (this.x - this.size <= 0) {
        this.velX = -this.velX;
    }

    if (this.y + this.size >= height) {
        this.velY = -this.velY;
    }

    if (this.y - this.size <= 0) {
        this.velY = -this.velY;
    }

    this.x += this.velX;
    this.y += this.velY;
};

Ball.prototype.collisionDetect = function () {
    for (let j = 0; j < balls.length; j++) {
        if (this !== balls[j]) {
            const dx = this.x - balls[j].x;
            const dy = this.y - balls[j].y;
            const distance = Math.sqrt(dx * dx + dy * dy);

            if (distance < this.size + balls[j].size) {
                balls[j].color = this.color = randomColor();
            }
        }
    }
};

// 定义EvilCircle
EvilCircle.prototype = Object.create(Shape.prototype);
EvilCircle.prototype.constructor = EvilCircle;

EvilCircle.prototype.draw = function() {
  ctx.beginPath();
  ctx.strokeStyle = this.color;
  ctx.lineWidth = 3;
  ctx.arc(this.x, this.y, this.size, 0, 2 * Math.PI);
  ctx.stroke();
};


function EvilCircle(x, y, exists) {
  Shape.call(this, x, y, 20, 20, exists);

  this.color = 'white';
  this.size = 10;
}
EvilCircle.prototype.checkBounds = function() {
  if((this.x + this.size) >= width) {
    this.x -= this.size;
  }

  if((this.x - this.size) <= 0) {
    this.x += this.size;
  }

  if((this.y + this.size) >= height) {
    this.y -= this.size;
  }

  if((this.y - this.size) <= 0) {
    this.y += this.size;
  }
};

EvilCircle.prototype.setControls = function() {
  window.onkeydown = e => {
    switch(e.key) {
      case 'a':
      case 'A':
      case 'ArrowLeft':
        this.x -= this.velX;
        break;
      case 'd':
      case 'D':
      case 'ArrowRight':
        this.x += this.velX;
        break;
      case 'w':
      case 'W':
      case 'ArrowUp':
        this.y -= this.velY;
        break;
      case 's':
      case 'S':
      case 'ArrowDown':
        this.y += this.velY;
        break;
    }
  };
};

// 定义 EvilCircle 冲突检测函数

EvilCircle.prototype.collisionDetect = function() {
  for(let j = 0; j < balls.length; j++) {
    if( balls[j].exists ) {
      const dx = this.x - balls[j].x;
      const dy = this.y - balls[j].y;
      const distance = Math.sqrt(dx * dx + dy * dy);

      if (distance < this.size + balls[j].size) {
        balls[j].exists = false;
        count--;
        para.textContent = '剩余彩球数：' + count;
      }
    }
  }
};


const balls = [];


while(balls.length < 25) {
  const size = random(10,20);
  let ball = new Ball(
    // 为避免绘制错误，球至少离画布边缘球本身一倍宽度的距离
    random(0 + size, width - size),
    random(0 + size, height - size),
    random(-7, 7),
    random(-7, 7),
    true,
    randomColor(),
    size
  );
  balls.push(ball);
  count++;
  para.textContent = '剩余彩球数：' + count;
}


let evil = new EvilCircle(random(0, width), random(0, height), true);
evil.setControls();

function loop() {
  ctx.fillStyle = 'rgba(0,0,0,0.25)';
  ctx.fillRect(0, 0, width, height);

  for(let i = 0; i < balls.length; i++) {
    if(balls[i].exists) {
      balls[i].draw();
      balls[i].update();
      balls[i].collisionDetect();
    }
  }

  evil.draw();
  evil.checkBounds();
  evil.collisionDetect();

  requestAnimationFrame(loop);
}

loop();